1. Field of the Invention
The present invention relates to a treatment method of semiconductor wafers and the like and a treatment system for the same; more specifically, the present invention relates to a treatment method of semiconductor wafers and the like, comprising a series of cleaning processes including a chemical process for removing dust, organic residues and inorganic residues or the like from surfaces of solid objects such as semiconductor silicon wafer, liquid crystal board and masking board by using several types of cleaning chemicals and a subsequent final water rinsing process (rinsing process) for rinsing off the cleaning chemicals from the object surface by using rinsing pure water, and a drying process of removing the rinsing pure water attached on the object surface, namely attached water (water drops) after completion of the final water rinsing process of the cleaning process, wherein these processes are carried out step by step in a sealed container. More specifically, the present invention relates to the improvement of a vapor treatment method and a treatment system for the same, wherein the removal of the attached water on the surface of the object is carried out at a drying process of mixing substitution using an organic solvent comprising a material readily mixable with the attached water and having a lower surface tension, for example IPA. (isopropyl alcohol).
2. Description of the Background Art
A variety of processes have been developed and proposed, conventionally, as a vapor treatment method comprising a series of cleaning processes from a chemical process for removing dust, organic residues or inorganic residues from the surface of the object by using several types of cleaning chemicals to a final water rinsing process for rinsing off the chemicals from the surfaces of the objects by using rinsing pure water, and a drying process of removing the attached water on the surfaces of the objects through mixing substitution with the vapor of an organic solvent, for example IPA (isopropyl alcohol), wherein these processes are carried out in a sealed container.
For example, these processes have been known, as described in published gazettes such as Japanese Patent Laid-open No. Sho 62-136825 (referred to as former, hereinbelow) and Japanese Patent Laid-open No. Hei 7-130699 (referred to as latter, hereinbelow).
According to the former vapor treatment process, however, an organic solvent in vapor is supplied from the top of a container into the container while rinsing pure water is pushed downward, to push out the water from the bottom of the container on completion of a series of rinsing processes. In other words, a pressure required to continuously supply an organic solvent vapor and to push down rinsing pure water and discharge the water from the bottom side of the container should be loaded appropriately, until the rinsing pure water is totally pushed down and discharged outside of the container. Because the former requires a vast amount of an organic solvent should be fed into the container per one drying process (per one cycle process), therefore, the former is disadvantageous and uneconomical from the respect of the cost. Because the organic solvent vapor should be fed into the container under a pressure required to push out rinsing pure water in the container, a gas pressuring means such as pump is essential.
According to the latter vapor treatment method, on contrast, the feeding of an organic solvent vapor into a sealed chamber is initiated, simultaneously when a object is drawn up from pure water in a rinsing tank, into the sealed chamber which is enclosing the rinsing tank, after the final water rinsing process of the cleaning process is performed in the rinsing tank fed with rinsing pure water, thereby condensation of the organic solvent vapor occurs on the surface of the object and the attached water is substituted with the organic solvent. In other words, the supply of the organic solvent vapor into the sealed chamber should be continued, at least until the object is completely drawn up from the pure water and the inside of the large sealed chamber is filled with the organic solvent vapor. Thus, like the former, the latter requires a vast amount of an organic solvent to be continuously supplied per drying process (per one cycle process), so that the latter is also costly and uneconomical.
The present inventors have therefore made various investigations. Consequently, the inventors have focused their attention to the fact that a part of an organic solvent fed into such container is condensed on the water surface, thereby forming a mixture layer of an appropriate thickness on the water surface, starting from the surface of the object toward the water surface; and that the concentration of the organic solvent in the mixture layer is lower on the side in contact to the water surface than on the side in contact to the object surface, which leads to the gradient of surface tension, and causes a liquid current from the object surface to the water surface. Thus, the inventors have achieved the present invention.
It is a purpose of the present invention to provide a treatment method and a system for semiconductor wafers and the like, capable of prominently reducing the use of an organic solvent per drying process (per one cycle process) at the vapor drying process of using an organic solvent.
It is another purpose of the present invention to provide a treatment method and system for semiconductor wafers and the like and capable of effectively and securely removing attached water from the surface of the object through the gradient of surface tension in addition to the mixing substitution with the organic solvent.
A still further purpose will be apparent in the detailed description and the drawings below.
These purposes can be attained by the treatment method and system for semiconductor wafers and the like in accordance with the present invention.
The treatment method of the present invention for semiconductor wafers and the like is including a series of processes from a cleaning process of an object to a drying process thereof in a sealed container and comprising a process of feeding warm pure water into the container where a plurality of sheets of the object are transferred and placed vertically in parallel arrangement, after the final water rinsing process of the cleaning process is completed, a process of feeding an organic solvent in vapor or fog at least into the upper space procured upward the fluid surface of the warm pure water in the container, a process of continuously feeding inert gas from the upper side of the container while the warm pure water is discharged under aspiration from the bottom side of the container after the supply of the organic solvent is terminated, and a process of drying the object comprising continuously reducing the pressure inside the container under aspiration, wherein the drying process of the object should be carried out under controls and regulations so that the pressure reduction in the container might be maintained at a preset pressure reduction degree at least untill the process of discharging the warm pure water from the bottom side of the container is completed.
The treatment system described above is characterized in that the water temperature of the warm pure water during feeding into the container is within a range of 30 to 65xc2x0 C.; the preset pressure reduction degree in the container is within a range of xe2x88x92350 mmHg to xe2x88x9250 mmHg until the completion of the discharge of the warm pure water under aspiration to the outside of the container; preferably, the water temperature of the warm pure water is within a range of 40 to 50xc2x0 C.; the pressure reduction degree in the container is preset within a range of xe2x88x92300 mmHg to xe2x88x92150 mmHg. The treatment system described above is characterized particularly in that the water temperature of the warm pure water is 45xc2x0 C. and the pressure reduction degree in the container is preset at xe2x88x92240 mmHg.
The treatment method described above is characterized in that the inside of the container is gas discharged under aspiration while feeding an organic solvent into the container. More specifically, the feeding of an organic solvent is continued, at least until the upper space inside the container is filled with the organic solvent. In other words, the feeding should be continued, until the organic solvent reaches all the exposed sheets of the object following the lowering of the fluid surface caused by the discharge of the warm pure water under aspiration.
The treatment method of the present invention is for semiconductor wafers and the like, including a series of processes from a cleaning process to a drying process in a sealed container, wherein a water rinsing process of the cleaning process is carried out at a state such that the feeding of inert gas into a container is initiated after a plurality of sheets of the object are transferred and placed vertically in parallel arrangement, and continued at least until the drying process is completed.
According to the treatment method of the present invention, hence, warm pure water within a range of 30 to 65xc2x0 C. is fed to a water level enough to immerse and sink the object in a container after a series of cleaning processes from the chemical process to the final water rinsing process are completed, whereby the object is heated to a necessary temperature around 30 to 65xc2x0 C. through the thermal energy of the warm pure water, which promotes drying at the drying process. Then, at a process of feeding an organic solvent in vapor or fog at least into the upper space procured upward the fluid surface of the warm pure water in the container, the pressure reduction in the container is maintained at a preset pressure reduction degree within a range of xe2x88x92350 mmHg to xe2x88x9250 mmHg until the discharge of the warm pure water under aspiration is completed, whereby the vapor or fog of the organic solvent fed into the container is condensed on the surface of the warm pure water to form a mixture solution layer, and alternatively, the vaporization or fogging is maintained, through the atmosphere inside the container under reduced pressure as maintained at a preset pressure reduction degree and through the thermal energy of the warm pure water, so that the vapor or fog is condensed on the surface of the exposed object following the lowering of the surface of the warm pure water, to be mixed and substituted with the attached water on the surface, and the attached water flows over the object surface in drops, together with the mixture solution of the attached water with the organic solvent, and is then removed from the object surface via the liquid current from the object surface toward the warm pure water surface, which current is developed in the mixture solution layer. More specifically, the object is dried, owing to the following two actions; the substitution action of mixing with the organic solvent and the action of liquid current developing in the mixture solution layer, which works to convey the attached water from the object surface toward the warm pure water surface. Then, the organic solvent is again vaporized from the mixture solution layer around the object, due to the atmosphere inside the container under reduced pressure which is maintained at a preset pressure reduction degree and due to the thermal energy of the warm pure water, so that the aforementioned condensation on the subject surface is repeatedly continued.
At a process of feeding the vapor or fog of the organic solvent into the upper space of the container while evacuating the container under aspiration, the vapor or fog of the organic solvent is smoothly introduced into the upper space of the container, whereby the upper space is filled with the organic solvent in a very short time. Thus, the transfer to subsequent processes smoothly progresses. Additionally, the organic solvent is vaporized at a temperature lower than the boiling point at atmospheric pressure (ambient pressure), because the pressure inside the container is appropriately reduced through evacuating under aspiration, whereby a solvent (vapor) atmosphere can be prepared in the upper space at a lower temperature.
The treatment system of the present invention is applied to semiconductor wafers and the like, which can carry out a series of cleaning processes including a drying process in a sealed container, comprising a container in a box form with a bottom and with an upper opening and of a size such that a plurality of sheets of the object can be transferred and placed vertically in parallel arrangement, and additionally with a sealing lid freely opening and closing on the upper opening; a liquid feeding means connected to the bottom side of the container to feed chemicals and pure water through a liquid feeding conduit into the container at least to a liquid level enough to immerse and sink the object by opening a chemical valve and a pure water valve, depending on each treatment stage from the cleaning process to the drying process and to feed warm pure water to the same level through a liquid feeding conduit by opening a warm pure water valve after completion of the rinsing process; a liquid discharging means connected at least to the liquid feeding means and the upper side of the container or the bottom side thereof, for liquid discharge under aspiration of the chemicals, pure water and warm pure water through a liquid discharge conduit by opening a liquid discharge valve from the container, depending on each treatment stage; a solvent feeding means connected to the upper side of the container to feed the vapor or fog of an organic solvent through a solvent feeding conduit into the container by opening a solvent valve; a gas feeding means connected to the upper side of the container to feed inert gas through a gas feeding conduit into the container by opening a gas valve; a detecting means mounted on the upper side of the container, to detect the pressure reduction in the container during the treatment stage for liquid discharge of warm pure water through the liquid discharge conduit connected to the bottom side of the container; a control means connected and arranged between the detecting means and the liquid discharge means or the gas feeding means, to perform a comparison process of the newly recovered pressure reduction output from the detecting means with the preset pressure reduction value and thereafter control the liquid discharge rate or the gas feeding rate on the basis of the process information, so that the pressure reduction in the container might be maintained at the preset pressure reduction value, until the liquid discharge of the warm pure water under aspiration is completed.
The treatment system described above is characterized in that the water temperature of the warm pure water during feeding into the container is within a range of 30 to 65xc2x0 C.; and that the preset pressure reduction value in the container is within a range of xe2x88x92350 mmHg to xe2x88x9250 mmHg, until the completion of discharging the warm pure water under aspiration to the outside of the container; preferably, the water temperature of the warm pure water is within a range of 40 to 50xc2x0 C.; and the pressure reduction in the container is preset within a range of xe2x88x92300 mmHg to xe2x88x92150 mmHg. The treatment system is characterized particularly in that the water temperature of the warm pure water is 45xc2x0 C. and the pressure reduction in the container is preset at xe2x88x92240 mmHg.
Accordingly, after transferring and placing a plurality of sheets of the object vertically in parallel arrangement from the upper opening into the container and closing then the upper opening with a sealing lid, the chemical valve, the pure water valve and the warm pure water valve at a water temperature within a range of 30 to 65xc2x0 C. are serially opened (in the serial order) depending on each treatment stage. Subsequently, the chemicals and pure water, and warm pure water are fed from the bottom side of the container through the liquid feeding conduit of the liquid feeding means into the container, to a final liquid level such that the object might be immersed and sunk therein, depending on each process stage from the cleaning process to the drying process, whereby an ascending liquid current of the chemicals and pure water, and warm pure water, flowing in contact to the subject surface, is formed in the container, for performing the treatment depending on each process stage. Then, the liquid discharge valve of the liquid discharge means connected to the upper side of the container is opened, so that excess chemicals and pure water, and warm pure water are discharged to the outside of the container under aspiration through the liquid discharge conduit.
On termination of the aforementioned processes, then, the solvent valve of the solvent feeding means is opened to feed the organic solvent in vapor or fog through the solvent feeding conduit at least into the upper space procured upward the surface of the warm pure water in the container. The feeding is continued until the upper space in the container is filled with the organic solvent in vapor or fog. By continuous aspirating the inside of the container by the liquid discharge means connected to the upper side of the container, then, the pressure inside the container is appropriately reduced, so that the organic solvent atmosphere is rapidly formed in the upper space in a short time. Because the pressure is also appropriately reduced in the solvent feeding means directly connected to the container, for example the inside of a vapor generation unit, following the pressure reduction in the container, the organic solvent is vaporized at a temperature lower than the boiling point at atmospheric pressure (ambient pressure) and is fed through the solvent feeding conduit into the container, so that a solvent atmosphere of such low temperature is formed in the container.
When the upper space in the container is filled with the organic solvent, the solvent valve is closed, while the liquid discharge valve of the liquid discharge means connected to the bottom side of the container is opened. Subsequently, the warm pure water in the container, passing through the liquid discharge conduit, is discharged under aspiration from the bottom side of the container to the outside of the container. Then, the pressure reduction in the container following the discharge of the warm pure water under aspiration is detected by the detecting means, and serially output to a control means, which performs the process of comparison between the current pressure reduction value in the container, which is detected by the detecting means, and the preset pressure reduction value within a range of xe2x88x92350 to xe2x88x9250 mmHg. Based on the process information, the discharge rate of the warm pure water through the liquid discharge means or the feeding rate of inert gas through a gas feeding means are adjusted and modified by the control means, whereby the inside of the container is maintained at the preset pressure reduction degree until the discharge of the warm pure water under aspiration is completed. More specifically, a part of the vapor or fog of the organic solvent fed into the container is condensed on the surface of the warm pure water to form a mixture solution layer on the fluid surface, while the vaporization or fogging is maintained in the container under the atmosphere of reduced pressure maintained at the preset pressure reduction via the thermal energy of the warm pure water, whereby the vapor or fog is condensed onthe surface of the exposed object as the liquid surface of the warm pure water is lowered, for substitution with the attached water on the subject surface. The attached water flows in drops over the surface of the object, together with the mixture solution of the attached water with the organic solvent, and the attached water is then removed fromthe object surface via the liquid current developing in the mixture solution layer from the surface of the object toward the water surface of the warm pure water. In other words, the object is dried through two actions, namely substitution action due to the mixing with the organic solvent and liquid current action developing in the mixture solution layer, which works to convey the attached water from the object surface toward the water surface of the warm pure water. Then, the organic solvent is again vaporized from the mixture solution layer around the exposed object, due to the atmosphere under reduced pressure and the thermal energy of the warm pure water, for repetitive condensation on the object surface.
After the warm pure water in the container is totally discharged under aspiration, then, the pressure inside of the container is kept reduced under continuous aspiration, in order to discharge all of the organic solvent, the mixture solution with the solvent, moisture and the like remaining in the container, to the outside the container. Subsequently, the inside of the container resumes atmospheric pressure (ambient pressure) due to inert gas fed from the upper side of the container into the container, followed by opening of the sealing lid and transferring of the object from the inside of the container to the outside thereof, whereby a series of processes from the cleaning process to the drying process are completed.